In the recent development of new medical drugs, combinatorial chemistry methods have been adopted in synthesizing candidate compounds. Combinatorial chemistry is the art of adopting combinations to synthesize a wide variety of compounds in a short time at one time. Compounds obtained by this method have a solubility problem in many cases. That is, in many cases, even if a compound is found to have excellent physiological activity in itself, if the compound has a property of being difficult to dissolve in water, development of the compound is abandoned. Even with compounds obtained by extraction from natural products, various organic syntheses are carried out and structural optimization is performed to improve solubility. Some medical drugs already on the market are also low in solubility. With such drugs, a medicament absorption amount varies within an individual patient and varies among individuals, and this places a large burden in terms of control of levels in blood, etc., on both a physician using a drug and a patient on whom the drug is used.
Microparticle formulations have received attention as a solution to the above problems. With a microparticle formulation, poorly-soluble medicament particles that are made no more than a micrometer in size are dispersed in water with stability. By using a microparticle formulation, a medicament can be increased in absorption rate and amount in a living body. Reduction in variation of absorption amount within an individual patient and among individuals and increase in effective availability with respect to a dose can also be anticipated. Inventions of methods for manufacturing such microparticle formulations are disclosed in Patent Documents 1 and 2.
With the invention disclosed in Patent Document 1, in order to finely pulverize a solid object, which is suspended in a solvent of a treatment target liquid without being dissolved, and thereby manufacture microparticles of the solid object, the treatment target liquid is irradiated with light of a predetermined wavelength, which is longer than an absorption band of the solid object, is in an absorption band of the solvent, and is absorbed by the solvent, to finely pulverize the solid object, and an irradiation intensity of the light irradiated on the treatment target liquid is made lower than an irradiation light intensity at which two-photon absorption occurs in the solid object.
With the invention disclosed in Patent Document 2, a solid object is finely pulverized by injecting water into an interior of a container in which the solid object is fixed to an inner wall and irradiating the solid object fixed to the inner wall of the container with light. In irradiation with the light, the light is irradiated from outside a region of the inner wall of the container at which the solid object is fixed to make the irradiated light propagate in the order of the container, the solid object, and the water so that microparticles can be formed at a fixed efficiency without lowering of efficiency of microparticle formation even in a state where the water contains a high concentration of microparticles.